The present invention relates to a wiping apparatus for wiping an excessive ink included in an ink supplied to a copperplate surface and attached to a portion except for a picture pattern in each printing cycle.
An intaglio printing press includes a copperplate cylinder on which a copperplate is mounted and an impression cylinder which is in contact with the copperplate. An image of an ink supplied to the outer surface of the copper plate is transferred to a sheet conveyed by a gripper of the impression cylinder from a sheet feeder through a swing pregripper, thereby performing printing. The printed sheet is conveyed by delivery chains and discharged.
A wiping apparatus is attached to an intaglio printing press of this type, as disclosed in Japanese patent laid-open (Kokai) No. 58-101060 and U.S. Pat. No. 3,762,319. The wiping apparatus includes a wiping roller rotated against the copperplate cylinder such that their surfaces travel in opposite directions, a plurality of brushes, pad surfaces of which are in contact with the surface of the wiping roller, and a doctor blade which is made of hard rubber and located downstream of the brush roller. The distal end of the doctor blade is in contact with the wiping roller. Of the ink supplied from the form roller of an inking apparatus to the copperplate surface, an excessive ink portion attached to portions around the recesses serving as a picture pattern is wiped by the wiping roller which is in rolling contact with the copperplate cylinder. Therefore, only the picture pattern of an ink applied to the recesses is transferred to the sheet. The wiping roller is dipped and rotated in a cleaning solution such as TRICLEN (tradename) stored in a cleaning solution tank. The ink transferred to the wiping roller by wiping can be removed by cleaning action of the cleaning solution and the brushes. The cleaning solution flowing along the circumferential direction of the wiping roller is removed by the doctor blade in the cleaning solution.
In ink wiping in such a wiping apparatus, if a contact pressure of the wiping roller abutting against the copperplate surface is excessively high, the ink in the recesses constituting the picture pattern is also removed. As a result, a very thin line cannot be printed. However, if the contact pressure is excessively low, the ink is left around the recesses, and the line width of the image is undesirably increased. As a result, the printed sheet blots. In addition, the ink is left on the entire surface of part of the non-picture pattern which results in poor appearance. In order to assure high quality of the printed matters, the contact pressure of the wiping roller abutting against the copperplate surface must be accurately adjusted. For this purpose, a conventional wiping apparatus includes a contact pressure adjusting unit.
A wiping roller contact pressure adjusting unit of this type is rotatably supported by wiping roller eccentric bearings, and these bearings are pivoted through a worm and worm wheel set or a screw shaft upon a manual operation with handles so that the wiping roller slightly comes close to or is slightly separated from the copperplate surface.
When the printing operation is temporarily interrupted, the printing cylinder is reset, and at the same time the wiping roller is separated from the copperplate surface. This operation is a manual operation in the conventional wiping apparatus and requires a skilled worker. Therefore, energy savings cannot be achieved. In addition, when the wiping roller is separated from the copperplate surface, the adjusted contact pressure is undesirably lost. When a printing operation is restarted, the contact pressure must be readjusted, thus resulting in time-consuming, cumbersome operations. It is also difficult to synchronize the right and left handles during the operation of the printing press.
When the contact pressure of the doctor blade is excessively high, the wiping roller is damaged. However, when the pressure is excessively low, the cleaning solution cannot be completely removed from the wiping roller to contaminate the copperplate surface. A conventional wiping apparatus includes a handle operated type contact pressure adjusting unit for moving the distal end of the doctor blade with respect to the surface of the wiping roller. The above-mentioned two adjusting units are used for attachment/detachment of the copperplate, the wiping roller, and the doctor blade.
However, in the conventional wiping apparatus described above, during interruption of the printing operation, when the eccentric bearings are operated with the corresponding handles to separate the wiping roller from the copperplate surface, the wiping roller is brought into contact with the doctor blade to damage the surface of the wiping roller. Therefore, detachment of the doctor blade comes first, thus degrading operability. If detachment of the wiping roller and then detachment of the doctor blade are performed, the surface of the wiping roller may be damaged by the distal end of the doctor blade. In addition, when contact pressure adjustment of the wiping roller is performed, a relative position between the wiping roller and the doctor blade is changed. The adjusted contact pressure of the doctor blade must be readjusted, resulting in time-consuming, cumbersome operations.
The doctor blade in the conventional wiping apparatus is held by a blade holder as an elongated plate-like holding member. The blade holder is fixed by a plurality of fixing screws to a fixing portion of the cleaning solution tank on the printing press side so that the holder is movable in the doctor blade attachment/detachment direction. A fine adjusting unit is arranged between the blade holder and the press-side fixing or support portion to move the blade holder relative to the fixing portion. During interruption of the printing operation, when the doctor blade is attached to or detached from the wiping roller, or when the contact pressure of the doctor blade with respect to the wiping roller is adjusted to prevent damage to the wiping roller and contamination of the copperplate surface by incomplete removal of the cleaning solution, the fixing screws must be loosened to cause the fine adjusting unit to move the blade holder. In addition, when the blade holder is removed so as to replace a doctor blade and brush pads with new ones, the fixing screws are fully loosened and the blade holder is removed.
In the conventional wiping apparatus, since the fixing screws are loosened with every movement of the blade holder, operability is degraded. In addition, the contact pressure of the doctor blade with respect to the wiping roller is changed before loosening and after fastening. For this reason, it is very difficult to adjust fastening of the fixing screws, requiring a skilled worker and resulting in a time-consuming operation. Furthermore, the removed fixing screws tend to be lost since they are separate members.